A plurality of mechanical actuators is used in motor vehicles, using which different operating parameters of the vehicle may be influenced. In order to ensure their performance reliability, these actuators have to be able to be checked. However, based on the increasing complexity of systems and components used in vehicles, a great depth of diagnostics is required for this. Fuel injection systems as well as the air system and the exhaust system of a vehicle without a doubt constitute a diagnosis area of concentration in this regard.
Malfunctions of actuators in the air system on internal combustion engines frequently lead, in an unrecognized manner, to an undesired performance reduction, increased fuel consumption, an overproportional increase in pollutant emissions as well as an increase in the wear of various assemblies during the operation of the internal combustion engine. In individual cases, the internal combustion engine may fail altogether. For this reason, methods are required for safely diagnosing possibly undetected malfunctions of actuators in the air system. This necessity comes about also with a view as to rising labor costs as well as the increasing complexity of assemblies used in motor vehicles which, when a fault in an individual assembly is not detected, may possibly have to be entirely replaced. Actuators in the air system of an internal combustion engine are located at various places and in different ways they influence the method of functioning of the entire system, this influence, as a rule, taking place in a manner not decoupled from the influence of other actuators in the air system. It is this circumstance that additionally complicates the search for faults with respect to malfunctions of actuators in the air system. At this time, and for that reason, reliable methods are not available for the detection of a defective, sticking or not completely closing actuator in the air system. Such actuators are located, for example, at the control flap (RKL), in the form of an exhaust gas recirculating valve (AGR), a swirl flap (EKAS) or for operating a turbocharger (VTG and WG). The actuators installed there may be restricted in their performance reliability or may fail completely, in the course of their operating life, for instance, by rusting or by wear.
Methods for diagnosing such functioning disturbances are based, these days, only on a simple motion test, in which the respective actuator is opened all the way and is subsequently closed again all the way. If possible, this motion test is supplemented by sight inspection, for a proper judgment of which, however, a good deal of experience is required if statements are to be made that go beyond the mere reaching of the end positions. A further possibility for fault analysis, during such a motion test, is in judging the noise emitted in each case by the internal combustion engine, for which, however, a lot of experience is also required, a subjective component always remaining, which the assessing person is never able to exclude. Indirect methods for assessing the functioning of actuators in particular, that is, for instance, noise analysis, always take place on the overall system, in this context, that is, a functional disturbance of an actuator to be analyzed, will have different effects as a function of the operating conditions under which the internal combustion engine is being operated, whereby in an analysis carried out in such a way, ambiguities may possibly remain which additionally make the fault diagnosis more difficult. It is possible, in particular, that a fault, that is to be diagnosed, is able to have different effects under different operating conditions, and this may lead to a wrong diagnosis.